The present invention relates to an electromagnetic fuel injection apparatus, an internal combustion engine having an electromagnetic fuel injection apparatus, and a drive circuit of an electromagnetic fuel injection apparatus. More particularly, the invention relates to an electromagnetic fuel injector comprising at least two coils for driving a valve body, and it also relates to an internal combustion engine having an electromagnetic fuel injector, and a drive circuit for an electromagnetic fuel injector.
An electromagnetic fuel injector (hereinafter simply called an injector) has a structure in which an electric signal is applied to a coil provided inside the injector, and, in response to a generated magnetic force, a plunger is moved to separate a valve body from a valve seat so that a fuel passage between the valve body and the valve seat is opened to allow fuel to be injected from a fuel injection orifice.
In the above-stated injector, as a means for forcing the valve body toward the valve seat in the closing direction, a return spring ember is provided, so that when application of the electric signal to the oil is stopped, the magnetic attraction force which moves the plunger in the opening direction is attenuated, and the fuel passage between the valve body and the valve seat is closed, namely the injector is closed.
In Japanese application patent laid-open publication No. Hei 8-326620, an electromagnetic fuel injector is disclosed, in which two coils are provided. At an initial stage of a valve opening operation, where a closed valve state is shifted to a valve opening operation application of electric signals to the two coils is performed; which, after the valve has opened, only one coil is energized to hold the valve open. In this conventional injector, each of the above-stated two coils is formed to have the same size and the same configuration. In this conventional injector, by the application of electrical signals to the two coils during the valve opening operation, the magnetic attraction force is made large and the valve opening delay can be shortened; and, during the time the valve is being held open, the magnetic attraction force is small, and so the valve closing delay time can be shortened.
In the conventional injector disclosed in Japanese application patent laid-open publication No. Hei 8-326620, as stated above, no consideration is given to the possibility that advantages can be achieved of the electric characteristic of the two coils is designated to be different from one another. For this reason, there are problems in that, when an attempt is made to assure a high speed response performance during valve opening, it is difficult to obtain a magnetomotive force necessary to maintain the valve in the open condition; on the other hand, when an attempt is made to assure a stable performance during the time the valve is held open, it is difficult to obtain a high speed response performance.
Accordingly, in the above-stated conventional injector, it is not easy to design a structure in which the high speed response performance is compatible with the stability performance during the time the valve is being held open for fuel injection.